大豆磷脂产品质量控制(Ⅲ)——水化油脚浓缩脱水对磷脂质量的影响

Quality Control of Soybean Phosphatide(Ⅲ) ——Effect of Dewatering stock after Degumming

水化油脚独特的流体特性导致在浓缩脱水时的困难。常用浓缩脱水有间歇浓缩脱水和连续浓缩脱水。间歇浓缩器的球形搅拌器采用热水加热 ,温度 70℃～ 80℃ ,不易造成磷脂的焦化。但时间长 ,处理量小 ,不易得到水分小于 1%的浓缩磷脂产品。有两种型号的连续薄膜蒸发器用于制取浓缩磷脂 ,立式薄膜蒸发器和卧式薄膜蒸发器。立式薄膜蒸发器由于磷脂粘度的变化易造成磷脂膜不连续 ,敏感性强。卧式薄膜蒸发器具有处理量大、时间短、可调节膜的厚度和容易控制的优点。一种能改善磷脂流动性又不损害磷脂质量的方法是提高浓缩器出口范围的温度。在水化油脚中添加油脂 ,可以避免水化油脚浓缩脱水的困难。在水化油脚进入浓缩器前 ,添加油脂 ,可以使由静电引起的粘度高峰提前出现 ,并远离浓缩器出口。

The unique rheology of the lecithin-water system has lead to processing difficulties in the drying of lecithin. Two types of dryer are used in lecithin processing. The first is a vacuum batch dryer equipped with rotating ball-shaped coils through which water circulate to maintain the lecithin at 70℃～80℃.Although this drying method minimizes charring, it suffers from long drying time and difficulties in consistently reducing the moisture levels to below 1%. The second type of dryer is continuous ,thin-film evaporators. There are two types, operating on the vertical or horizontal axis. Vertical thin film evaporators can work very well but are more sensitive because the lecithin film can break within the apparatus as the viscosity of the lecithin gum increases. Horizontal film evaporators have the following advantages: large capacity per unit area; short drying time; adjustability of thickness of film; adequate process control. One method to improve fluid flow without compromising product quality would be to confine process temperature in creases to around the evaporator outlet. The difficulties associated with lecithin gum drying may be avoided by the addition of oil prior to entering the evaporator. An increased oil content ensures that the electrostatic-induced viscosity perk occurs at a higher moisture level and at a grater distance from the dryer outlet in a vertical scraped surface evaporator.